1. Field of the Invention
The present invention relates to an image forming apparatus and is preferably applied to, for example, an electrophotographic image forming apparatus, such as a printer, a facsimile machine, or a copier, having a density correction function.
2. Description of the Related Art
There is a conventional image forming apparatus including: an image forming unit for forming an image with developer, such as toner; a transfer unit for transferring the image (also referred to as the developer image) formed by the image forming unit onto a recording medium, such as a sheet of paper; and a conveying unit including a belt for conveying the recording medium.
The conventional image forming apparatus performs density correction by forming a test pattern (referred to below as the density correction pattern) for density correction on the conveying unit and reading the density correction pattern by a density correction sensor when the image forming apparatus is started or between print jobs (i.e., when no printing is performed).
Japanese Patent Application Publication No. 2006-227336 discloses an image forming apparatus including a conveying member for conveying a recording medium in a conveying direction, the conveying member having a width (a length in a direction across the conveying direction) greater than that of the recording medium; an image forming unit for forming an image on the recording medium; an image forming processor for causing the image forming unit to form a density detection image outside the recording medium on the conveying member; a sensor for detecting the density of the density detection image; and a density correction processor for performing density correction based on the detected density. With this configuration, when the image forming apparatus prints on a long recording medium, such as a recording medium web from a roll of recording medium or a paper web from a roll of paper, it can perform density correction during the printing.
However, the above image forming apparatus forms the density detection image outside the recording medium in the width direction of the recording medium to perform density correction during printing. Thus, the conveying member and image forming unit need to have widths sufficiently greater than the width of the recording medium. This increases the size of the image forming apparatus.